explain_setpriority man page

explain_setpriority — explain setpriority(2) errors

Synopsis

#include <libexplain/setpriority.h>

const char *explain_setpriority(int which, int who, int prio);
const char *explain_errno_setpriority(int errnum, int which, int who, int prio);
void explain_message_setpriority(char *message, int message_size, int which, int who, int prio);
void explain_message_errno_setpriority(char *message, int message_size, int errnum, int which, int who, int prio);

Description

These functions may be used to obtain explanations for errors returned by the setpriority(2) system call.

explain_setpriority

const char *explain_setpriority(int which, int who, int prio);

The explain_setpriority function is used to obtain an explanation of an error returned by the setpriority(2) system call. The least the message will contain is the value of strerror(errno), but usually it will do much better, and indicate the underlying cause in more detail.

The errno global variable will be used to obtain the error value to be decoded.

which
The original which, exactly as passed to the setpriority(2) system call.
who
The original who, exactly as passed to the setpriority(2) system call.
prio
The original prio, exactly as passed to the setpriority(2) system call.
Returns:
The message explaining the error. This message buffer is shared by all libexplain functions which do not supply a buffer in their argument list. This will be overwritten by the next call to any libexplain function which shares this buffer, including other threads.

Note: This function is not thread safe, because it shares a return buffer across all threads, and many other functions in this library.

Example: This function is intended to be used in a fashion similar to the following example:

if (setpriority(which, who, prio) < 0)

{

fprintf(stderr, "%s\n", explain_setpriority(which, who, prio));

    exit(EXIT_FAILURE);
}

The above code example is available pre-packaged as the explain_setpriority_or_die(3) function.

explain_errno_setpriority

const char *explain_errno_setpriority(int errnum, int which, int who, int prio);

The explain_errno_setpriority function is used to obtain an explanation of an error returned by the setpriority(2) system call. The least the message will contain is the value of strerror(errno), but usually it will do much better, and indicate the underlying cause in more detail.

errnum
The error value to be decoded, usually obtained from the errno global variable just before this function is called. This is necessary if you need to call any code between the system call to be explained and this function, because many libc functions will alter the value of errno.
which
The original which, exactly as passed to the setpriority(2) system call.
who
The original who, exactly as passed to the setpriority(2) system call.
prio
The original prio, exactly as passed to the setpriority(2) system call.
Returns:
The message explaining the error. This message buffer is shared by all libexplain functions which do not supply a buffer in their argument list. This will be overwritten by the next call to any libexplain function which shares this buffer, including other threads.

Note: This function is not thread safe, because it shares a return buffer across all threads, and many other functions in this library.

Example: This function is intended to be used in a fashion similar to the following example:

if (setpriority(which, who, prio) < 0)

{
    int err = errno;

fprintf(stderr, "%s\n", explain_errno_setpriority(err, which, who, prio));

    exit(EXIT_FAILURE);
}

The above code example is available pre-packaged as the explain_setpriority_or_die(3) function.

explain_message_setpriority

void explain_message_setpriority(char *message, int message_size, int which, int who, int prio);

The explain_message_setpriority function is used to obtain an explanation of an error returned by the setpriority(2) system call. The least the message will contain is the value of strerror(errno), but usually it will do much better, and indicate the underlying cause in more detail.

The errno global variable will be used to obtain the error value to be decoded.

message
The location in which to store the returned message. If a suitable message return buffer is supplied, this function is thread safe.
message_size
The size in bytes of the location in which to store the returned message.
which
The original which, exactly as passed to the setpriority(2) system call.
who
The original who, exactly as passed to the setpriority(2) system call.
prio
The original prio, exactly as passed to the setpriority(2) system call.

Example: This function is intended to be used in a fashion similar to the following example:

if (setpriority(which, who, prio) < 0)

{
    char message[3000];

explain_message_setpriority(message, sizeof(message), which, who, prio);

    fprintf(stderr, "%s\n", message);
    exit(EXIT_FAILURE);
}

The above code example is available pre-packaged as the explain_setpriority_or_die(3) function.

explain_message_errno_setpriority

void explain_message_errno_setpriority(char *message, int message_size, int errnum, int which, int who, int prio);

The explain_message_errno_setpriority function is used to obtain an explanation of an error returned by the setpriority(2) system call. The least the message will contain is the value of strerror(errno), but usually it will do much better, and indicate the underlying cause in more detail.

message
The location in which to store the returned message. If a suitable message return buffer is supplied, this function is thread safe.
message_size
The size in bytes of the location in which to store the returned message.
errnum
The error value to be decoded, usually obtained from the errno global variable just before this function is called. This is necessary if you need to call any code between the system call to be explained and this function, because many libc functions will alter the value of errno.
which
The original which, exactly as passed to the setpriority(2) system call.
who
The original who, exactly as passed to the setpriority(2) system call.
prio
The original prio, exactly as passed to the setpriority(2) system call.

Example: This function is intended to be used in a fashion similar to the following example:

if (setpriority(which, who, prio) < 0)

{
    int err = errno;
    char message[3000];

explain_message_errno_setpriority(message, sizeof(message), err, which, who, prio);

    fprintf(stderr, "%s\n", message);
    exit(EXIT_FAILURE);
}

The above code example is available pre-packaged as the explain_setpriority_or_die(3) function.

See Also

setpriority(2)
set program scheduling priority
explain_setpriority_or_die(3)
set program scheduling priority and report errors

Referenced By

explain(3), explain_setpriority_or_die(3).